Metallic-Nonmetallic Phase Coexistence above the Consolute Point of Sodium-Ammonia Solution

Abstract

The heat capacity under saturated vapors, ${C}_{\ensuremath{\sigma}}$, of three different concentrations of NaN${\mathrm{H}}_{3}$ solution ($X=0.045, 0.046, 0.063$ molar part of Na) has been measured in the temperature range 200-300 K. All three ${C}_{\ensuremath{\sigma}}(T)$ curves show anomalies consistent with the existence of a new two-phase region above the well-known liquid-liquid critical point (${X}_{c}=0.0415$, ${T}_{c}=232$ K). Its location is compatible with the metal-nonmetal transition line; so it is believed that in equilibrium these are metallic and insulating phases with different concentrations of electrons.